Constant intensity illumination system



Feb. 18, 1936. i w A ER 2,030,854

CONSTANT INTENSITY ILLUMINATION SYSTEM Filed March 50, 1933 lN vENTOR 'Geo ye Q Z Calver ATTORNEY mama Feb. 18,1936

UNITED STATES CONSTANT INTENSITY mumna'rron svs'ram George W. Oalvcr, United States Navy.

Application March so, 193:, Serial No. seas- 1 "ZCIaimS.

(Granted under the act of March 3, 1888, as

amended April 30, 1928; 370 O. G. 75'!) This invention relates to a system of illumination, more particularly to an automatic system wherein the intensity of illumination within a' compartment is kept relatively constant regardless of changes in the natural or daylight illumination. 2',

During ordinary daylight conditions it is seldom if ever necessary to supplement the natural light with artificial light in a room where suflicient a windows have been provided. However, due to the presence oi clouds, rain, snow, smoke, etc., it is often necessary to supplement the natural light with artificial light or to provide illumination that is wholly artificial.

g This invention has for one oi its principalob- Jects the provision of a method of and an apparatus mautomatically maintaining the intensity of illumination within a room or other compartment at a predetermineddesired level irrespecno tive of variations in the natural illumination.

Another object oi! this invention is to provide a system of illumination wherein the intensity to be automatically maintained may be manually selected so that any desired intensity in keeping I! with the work to be done thereby may be obtained. With the above and other objects in view, this invention consists in the construction, combination and arrangement of parts as will be described more fully hereinafter. so In the drawing:

Fig. l is a diagrammatic view of one embodiment of my invention;

Fig. 2 is a plan view or a room having windows on only one side showing one manner or distrib- 88 um the artificial lamps according to this inventlon.

Fig. 1 or the drawing shows a photo-electric cell I having cathode 2 and anode 3 :onnected to a source of potential I by means of a high resist- 40 ance I. The photo-cathode I is connected by means of a resistance II to the grid or control element Q of a thermionic tube 6. The plate or anode I 01' tube 6 is connected to the positive lead of the battery or other source of potential 48 4'. The negative terminal of battery I is connected to the brush I! or the double armature motor I6. The cathode I of tube lis energized by an appropriate source of potential shown at ii. The grid 8 oi the tube is connected through resistance so 'i\ and battery I! or other source of direct current potential to the cathode 9. The cathode 8 is further connected to brush it of double armature motor Ii. The field oi the double armature motor I. is shown at H and is excited by battery ll through an appropriate control resistance. The

battery I8 is also connected through rheostat I. to brushes 20 and- 2| which cooperate with the commutator on the opposite end of the shaft from the one with which brushes l4 and i cooperate.

. The armature of motor I8 is mounted on the shaft 5 22 which is suitably supported by bearings. Attached to one end of shaft 22 is a worm 23 which cooperates with a worm gear 24 to drive a shaft 24' which is supported in suitable bearings.

. Mounted on shaft 24' is a non-conducting cylin- 1o der ii that is partially covered by a conducting portion 26 that extends about the cylinder to form a conducting portion thereon that intercepts a continuously varying angle from one end to the other. The conducting portion 26 ot the cylinder is connected to a slip ring 21 and a brush 2! is adapted to contact therewith. The brush 28 is connected by lead 29 to one o! the terminals 0! a suitable source of electric current, while the conductor 30 is connected to the other terminal. go Cooperating with the contacting member 26 are a series of brushes 38, 31, 3B, 39, and 40 each of which is connected to one terminal of the lamps 3|, 32, 33, 34, and", respectively. The remain- I ing terminals of the lamps are connected to the g5 conductor 30.

In Fig. 2 the arrangement of the lamps II to inclusive is shown. In this figure each of the reference characters 3| to 35 denotes a row of lamps extending across the room parallel to the 30 side of the room having windows. The lamps are arranged so that they are not exactly opposite the windows whereby little of the direct illumination from these lamps will pass out o! the room through the windows.

The above described system operates in the following manner: First, it is assumed that the daylight coming through windows 42 is sufllcient to provide the desired intensity of illumination throughout the whole room. In this case none 01' the lamps ii to 35 inclusive would need to be illuminated. Now assume that it became very cloudy and the intensity 0! illumination within the room 43 became so low that additional illumination would be desirable. The photo-electric 45 cell i would cease to conduct suflioient current to maintain a potential drop across the resistance 5 to keep the-grid l at a sufficient positive potential to allow a sutficient' amount of plate or anode current to flowthrough the circuit including the anode I, battery 4; brush i5, and the cooperating armature winding of double armature motor ltbacktothe brush it andthenee totho cathode to overcome the field created by the other armature winding-connectcdto brushes II and 56 2|. Themotor armatm-e ll wouldthenturnin a direction such as to rotate the cylinder ll until sufllcient or the contacts 38, 31, etc. are in con- .tact with the conducting segment 20 to complete the circuit of a sumcient number of the lamps ll, 32, etc. to bring the illumination intensity to the desired value. .Assuming next that the cloud passes'on and the illumination intensity from the sky and sun furnishes sufiicient light within the room 43 that the lamps are no longer necessary; The increased illumination would render the photo-electric cell i conducting to such a degree that a considerable potential drop would exist across the extremities of the resistance 5. This potential drop across the resistances would raise the potential of the photo-cathode 2, thereby decreasing the negative potential normally on the gridt of thetube i duetobattery-ll andresult in a large plate current fiow in the plate circuit of the tube 6. This plate current flowing .through the-armature winding connected to brushes I4 and I5 of the double armature motor ll would tendtomagnetizethearmatureinadirectionso as to oppose the magnetizing eiiect of the winding connected to brushes II and II. When the current flowing through the armature winding connected to brushes I4 and It becomes suiiiciently great, it will overcome the effect of the other winding and cause the armature of the motortorotateintheoppositedirectiontothedirection of rotation when the winding connected to brushes 20 and 2| only is energized. 'Ihe worm gear 24 would then cause cylinder 4| to be rotated in the opposite direction, cutting out the lamps ll, 32, 33, II, and 35 in the inverse order in which they were illuminated until such an intensity 'of light is again obtained in the room that the double wound armature motor I has no tendency to rotate.

Thebatteryll inthegridcircuitoftubeiis ofsuch a value and is so poled that the grid i is normally maintained at its cut-0d point and no current will flow in the plate circuit through one of the armature windings of the motor ll.

Under such conditions, the other armature of the motor It would give rise to the only turning torque in the motor which would tend to make the motor rotate in such a direction as to cut in some of the lamps. An adjustable frictional load is applied to the shaft 24' by means of the prony 25 to prevent any tendency of the device to hunt. In operation, the load applied by the prony II serves to act as a time delay device to prevent any of the lamps from being turned on or 01! due to extremely minute light intensity changes on the cell I.

A stop device is provided at M on the cylinder II which engages with the fixed lug 44' for preventing the shaft 24' from making a full revolution. When shaft 24' has turned to either of the extreme positions, representing all lights on or all lights oil, it is stopped by the stop device 44 which coacts with lug ll.

A graduated light filter is shown at I. This filter may or may not be used, depending upon the service for which the system is intended. In case it is desirable to have the room illuminated at one constant intensity and it is never desired to have any other degree of illumination, the graduated filter 45 may be dispensed with. The graduated filter beginning at one end is transparentandchanges,asalightwedge,tobecome opaque at the opposite end. By adjusting the graduated filter longitudinally so that therays .oilightfromtheroomwill'bemadetopass' through a selected portion of the-filter more entering the photo-electric cell I, it is possible to adjust the intensity at which the illumination v of the room is to be maintained.

It is not intended to limit' the invention to the specific mechanism disclosed inasmuch as it is: possible to vary from the embodiment shown by;

For instance, a

other and equivalent means. photo-resistive or photo-voltaic cell or the like vmay be used in place of the photo-electric cell I.

Also, a grid glow tube or double grid tube or other typeoftubeorrelaymaybeusedinplace oi the conventional three-element tube shown in Fig. 6;

and several amplifier stages or relays may be used imteadiof the single stage shown in the drawing. The armature windings connected to the commutators on shaft 22 may be wound in different slots or in the same slots or extend for thefulllength ofthearmatureorforonlyaportlon thereof. The field ll may be made in one or two parts, while the worm gear speed reducing device shown at 28 and II may be replaced with any appropriate type of gear reductiometc.

In the above description the terms "light" and I upon undesired organisms. Obviously-if natural illumination is deficient in only portions of the desired spectrum it will be desirable'to provide lamps that emit only such portions. v

The invention described herein may be manufactured and used by or for the Government of the United Statesof America for governmental purposes, without the payment of any royalty thereon.

I claim:

l. A system for maintaining the intensity of illumination substantially constant over a predetermined area notwithstanding wide variations in the uncontrolled components of the illumination, comprising, a plurality of lamps, asource of power for energizing said lamps, a. multi-position switch for connecting all or a part of said lamps in circuit with said source of .power, means for urging said multi-position switch toward the position in which all of said lamps are connected in circuit with said source of power, a light sensitive device, means controlled by saidllight sensitive-device for urging said multi-position switch toward the position in which none of said lamps are connected in circuit by a force proportional to the illumination on said device, whereby the forces tending to urge said multi-position switch in opposite directions are balanced at the position of the multi-positlon switch in which the uncontrolled components of illumination are supplemented by just the proper amount oi illumination from said lamps to providea predetermined desired intensity of illumination over said area, and an adjustable light filter over said light sensitive device whereby said system may be adjusted to maintain any predetermined intensity of illumination.

2. A system for maintaining the intensity of illumination substantially constant over a. predetermined area notwithstanding wide variations in the uncontrolled components of 'the'illumination, comprising a plurality of lamps, a-source of power for energizing said lamps, a multi-positlon switch for connecting all or apart of said lamps in circuit with said source of power, means for urging said muiti-position switch toward the poaitioninwhichfllofnidlnmpsareeonneeted inch-cult withaidaonreeotpowereomnflain: an electric motor having s field winding and twoumaturewindinmtheiieldwindinzandone umahirewindinzotwhichnreeonnectedton source of potential, I. lilht sensitive devieeand means controlled by said light sensitive device 101' applying an electric cunentto the other of leidarmaturewindinatorurzincaidmnlti-pod theuneontroiledottheflllminetionis 5 mpplementedbylizhttromsaidhmpebyw sumclent unount to mnlntein the illumination eomtlnt.

mm] W. CALVIR. 

